<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link rel="stylesheet" href="./styles/index.css" />
    <title>Document</title>
  </head>
  <body>
    <div id="app" class="score-case">
      <div class="table">
        <table>
          <thead>
            <tr>
              <th>编号</th>
              <th>科目</th>
              <th>成绩</th>
              <th>操作</th>
            </tr>
          </thead>
          <tbody>
            <tr v-for="v, i in list" :key="v.id">
              <td>{{ i + 1 }}</td>
              <td>{{ v.subject }}</td>
              <td :class="{ red: v.score < 60 }">{{ v.score }}</td>
              <td><a href="#" @click.prevent="del(v.id)">删除</a></td>
            </tr>
          </tbody>
          <tbody v-show="list.length === 0">
            <tr>
              <td colspan="5">
                <span class="none">暂无数据</span>
              </td>
            </tr>
          </tbody>

          <tfoot v-show="list.length > 0">
            <tr>
              <td colspan="5">
                <span>总分：{{ totalScore }}</span>
                <span style="margin-left: 50px">平均分：{{ avgScore }}</span>
              </td>
            </tr>
          </tfoot>
        </table>
      </div>
      <div class="form">
        <div class="form-item">
          <div class="label">科目：</div>
          <div class="input">
            <input
              type="text"
              placeholder="请输入科目"
              v-model.trim="subject"
            />
          </div>
        </div>
        <div class="form-item">
          <div class="label">分数：</div>
          <div class="input">
            <input
              type="text"
              placeholder="请输入分数"
              v-model.number="score"
              @keyup.enter="add"
            />
          </div>
        </div>
        <div class="form-item">
          <div class="label"></div>
          <div class="input">
            <button class="submit" @click="add">添加</button>
          </div>
        </div>
      </div>
    </div>
    <script src="https://unpkg.com/vue@2.7.14/dist/vue.js"></script>

    <script>
      const app = new Vue({
        el: '#app',
        data: {
          list: [
            { id: 1, subject: '语文', score: 20 },
            { id: 7, subject: '数学', score: 99 },
            { id: 12, subject: '英语', score: 70 },
          ],
          subject: '',
          score: ''
        },

        computed: {
          totalScore() {
            return this.list.reduce((sum, v) => sum + v.score, 0)
          },
          avgScore() {
            return this.totalScore / this.list.length
          }
        },

        methods: {
          add() {

            if (this.subject === '' || this.score === '') {
              alert('请将表单填写完整')
              return
            }

            const nextId = Math.max(0, ...this.list.map(v => v.id)) + 1
            this.list.push({ id: nextId, subject: this.subject, score: this.score })

            this.subject = ''
            this.score = ''
          },
          del(id) {
            this.list = this.list.filter(v => v.id !== id)
          } 
        }
      })
    </script>
  </body>
</html>
